1. Field of the Invention
The present invention relates to hydraulic assistance devices and more particularly to such devices intended for a brake circuit operating both hydrodynamically (more commonly known as full-power operation) and hydrostatically.
2. Brief Description of the Prior Art
The document FR-1-1,479,746 discloses a hydraulic brake booster of the full-power type which is provided for operating the control system of the clutch of a vehicle and which comprises a piston means having a valve for controlling high-pressure fluid capable of being actuated by the clutch pedal via a push-rod. When there is a failure in the high-pressure circuit, the piston means is able to move, thus allowing the push-rod to operate as the piston of a conventional master cylinder, and to thus create a standby hydrostatic pressure. However, since the diameter of the push-rod is small, the volume of fluid displaced by the push-rod is limited and therefore the device cannot be used for a vehicle brake system.